A synthetic trans-3,4-dimethyl-4-(3-hydroxyphenyl) piperidine with peripherally selective opioid mu receptor antagonist activity. Alvimopan is a selective and competitive antagonist at mu-opioid receptors, found in myenteric and submucosal neurons and the immune cells of the lamina propria in the human gut. Upon administration, this agent binds to mu-opioid receptors in the gut, thereby reversing opiod-related disturbances in gut motility. Alvimopan is approximately three to nine times more potent than naloxone. Check foractive clinical trials using this agent.